In general, a system for driving a motor may include a power storage device (e.g., battery), an inverter for converting DC power stored in the power storage device into 3-phase AC power for driving a motor, the motor, a controller for controlling switching of the inverter on the basis of a current command generated on the basis of a torque command for driving the motor and a measured current actually provided to the motor.
Here, the inverter includes a plurality of switching elements, and these switching elements may be controlled according to pulse width modulation (PWM) to generate AC power. The AC power generated through the inverter is provided to the motor such that the motor is driven.
When a pulse width modulation signal for controlling the switching elements in the inverter has a fixed frequency, control is simplified to improve controllability and to achieve stabilized control of a motor driving system. On the other hand, when the inverter is controlled according to the pulse width modulation signal at a fixed frequency, strong harmonic components appear in a band corresponding to an integer multiple of the switching frequency, causing electromagnetic noise and vibration.
To solve the disadvantage caused by the pulse width modulation signal having a fixed switching frequency, a random pulse width modulation (RPWM) method which instantaneously disperses a switching frequency band is known. When the RPWM method is applied, noise or vibration can be suppressed through energy distribution but controllability deteriorates because a switching frequency randomly changes. Further, when the RPWM method and other modulation methods applied to a 6-step control technique using 12-sample phase control are switched each other, the switching frequency rapidly changes, deteriorating current controllability of an inverter.
The details described above as background art are for providing a thorough understanding of the present disclosure, and it will be apparent to those skilled in the art that the present disclosure may be practiced without such specific details.